Cory Booker had the most to lose in last night’s Democratic debate for U.S. Senate candidates – but he may have gained the most, possibly even winning it outright.

In a 90-minute debate that was heavy on foreign policy questions, the Newark mayor proved more than adept at talking international affairs, from Syria to China. He even parried one question about China into a chance to talk about job growth in Newark.

And when it came to domestic affairs, he barely took a hit – at least not the kind that may make a significant difference -- from his three challengers.

Distinctions were drawn, to be sure, as U.S. Reps. Rush Holt and Frank Pallone and New Jersey Assembly Speaker Sheila Oliver each tried to put a dent in Booker’s front-runner status – not to mention his commanding, if not overwhelming, lead in the polls.

The issue of education was probably the closest any of them came, with the two congressmen each calling Booker out on his early support for private school vouchers – adding a few digs at Gov. Chris Christie as well.

“I would like to know how vouchers would help the Newark schools. They just siphon money away,” Holt said. “And the massive expansion of charter schools is not the answer to an excellent education for 50 million schoolchildren.”

“Cory Booker has been a vigorous supporter of Gov. Christie’s education policies,” he said.

Booker initially ducked the voucher issue entirely, talking instead about his support for Newark school reforms that had nothing to do with vouchers. But even when he did address it, he came back to say that both Holt and Pallone had supported a similar voucher program in Washington, an assertion that only Holt refuted.

Oliver also criticized the state’s ongoing operation of three districts, including Newark, and its fledgling takeover of Camden schools. Booker has supported the state’s role in Newark, especially backing Christie’s choice of school superintendent, Cami Anderson.

“Since we are talking about troubled districts, Newark has to come into the discussion,” Oliver said. “Under the state’s auspices, we have seen no improvement in the schools whatsoever.”

Pallone kept pressing the difference in experience, too, saying that Booker’s lack of a legislative track record ran against the mayor’s claims – and prolific television advertising -- that he can reach across party lines.

“I think we need an experienced legislator,” Pallone said. “Being a mayor is not the same as having been in Congress.”

Booker shot back that the lack of Washington experience was more of an asset, not a liability.

“I think you have seen two types of leadership tonight,” Booker said in his closing remarks. “The two congressmen here have 40 years of experience, and if you want that kind of experience and are happy with it, you should vote for that.

“But to me, we don’t need that kind of experience, we need a different kind of experience in Washington,” he said.

The debate was held at Montclair State University, with NJTV news host Michael Schneider and Bergen Record editorial page editor Alfred Doblin serving as moderators.

This was the first debate where all four candidates participated. The four are expected to participate in the final debate on Thursday, the last one before the Democratic primary on Aug. 13.

The two Republican candidates – Steve Lonegan and Alieta Eck – last week held their lone debate before the GOP primary next Tuesday.

The Democratic and Republican nominees will then face each other in the Oct. 16 special election to fill the seat left vacant by the death of U.S. Sen. Frank Lautenberg in June.